A 'Greatest' Generation: Linking Personality, ErasHow much does the era you grow up in affect your personality? Psychologist Jean Twenge, a researcher at San Diego State University believes that a key factor in determining primary character traits is the generation that people are born in — and there may be credence to the notion of "The Greatest Generation."

In a few minutes rock and roll superstars, if you're five years old, hey, hey, it's the Wiggles.

BRAND: But first: Generation X, Generation Y, Baby Boomers. Seems like every few years we name and brand a new generation. But how much do people really change from decade to decade?

In a study out this month, a psychological researcher has done a kind of cross-generational comparison that has never been done before. Reporter Alix Spiegel has the story.

(Soundbite of music from "Saving Private Ryan")

ALIX SPIEGEL reporting:

As far as stories of the greatest generation go, Saving Private Ryan is pretty standard. You know noble self sacrifice is on the menu the minute you hear the solemn tones of the trumpet, and sure enough two minutes later there's Tom Hanks squinting into the morning light offering steady advice to a boat full of men in fatigues.

(Soundbite of movie "Saving Private Ryan")

Mr. TOM HANKS: (as Captain John H. Miller) Go back and clear those murder holes. I'll see you on the beach.

SPIEGEL: The following 170 minutes are devoted to the well-tread idea that this was a group of men with uncommon personal strength, a generation of square jawed determination. But are the members of the so-called greatest generation really so different from we poor schleps born after the invention of the hula hoop? Of is that idea, that earlier generations were somehow different, simply gauzy nostalgia, and human beings are equally noble and selfish, introverted and extroverted, no matter our time or culture?

How would you even begin to measure personality differences between generations?

Ms. JEAN TWENGE (Psychologist, San Diego State University): I am a special person. If I ruled the world it would be a better place, and I can live my life any way I want to.

SPIEGEL: This is San Diego State University psychologist Jean Twenge reading from a list of questions on the narcissistic personality inventory, a 40 item personality test that's been used since the 1960's.

What Twenge has done with this test, and a raft of other personality scales featured in her new book Generation Me, has never been done before. By using a computer program called the Web of Knowledge she tracked down every time a given personality test, the narcissistic personality inventory, say, has been used over the past 40 years.

She then poached the data from the study and used it to construct a real cross-generational analysis of personality. The advantage of this method was that she was able to compare people who took the exact same test at the exact same age in different decades. She looked at everything from altruism to anxiety, and she claims 1.3 million people, and her results are surprising.

Ms. TWENGE: I believe that there has been a fundamental shift in several personality traits across the generations.

SPIEGEL: Take, for example, self esteem. Twenge looked at scores from a test called the Rosenberg Self Esteem Scale. Apparently the Rosenberg has been passed out to college students on a regular basis since the '60s. So by comparing the scores of students from the Kennedy Administration to the Reagan Era, Twenge was able to document that there have been real and substantial increases in self esteem.

Likewise, she says, narcissism has grown, and, says Twenge, there are changes in even more basic personality traits.

Ms. TWENGE: In personality research it's fairly well agreed that there are a Big Five personality traits: extroversion and neuroticism are two of those traits and those are two traits that have both shown a standard deviation shift.

SPIEGEL: In fact, according Twenge, it's hard to find a personality trait that hasn't changed.

Ms. TWENGE: I'm trying to think if there's anything I looked at the just was completely flat and I can't think of anything.

SPIEGEL: All of which has led Twenge to this pretty startling conclusion.

Ms. TWENGE: When you are born has more influence over your personality than the family you grew up with.

SPEIGEL: To be clear, it's not that parents don't influence the personality of their children, Twenge says genetics plays an enormous roll in determining how people turn out, but according to Twenge, studies of twins separated at birth consistently indicate that family environment accounts for at most five percent of variance in personality traits.

Ms. TWENGE: They found that over and over with twin studies and other sources, that individual family environment really doesn't explain much variance, and in these studies that I've done, over and over that generational change tends to explain ten to 20 percent, in other words two to four times more variants than the family environment.

SPIEGEL: But Robert McCray, a world respected researcher who spent a career studying personality, is skeptical of Twenge's findings.

He points to years of his own cross-cultural research on personality, which suggests that not only is generation not that important, but something as basic as culture hardly makes a dent.

Mr. ROBERT MCCRAY (Researcher): We've got data from over 50 cultures around the world and one sees the same personality traits everywhere.

There are some slight differences, but they're fairly small.

SPIEGEL: In other words, no matter what Twenge's research suggests people are simply people, the same old thing from Rome to Richmond, Virginia.

NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.